Lean Spool

[Scott@FP]

Sometimes you'll see issues, sometimes not. Had a 4 cyl that had a waste spark CDi incorrectly wired that fired all 4 plugs every TDC and BDC, NEVER backfired!

Keep in mind a La sensor is not telling you what happens inside the combustion chamber during combustion, but what is present in the exhaust stream at the sensor location, it can and will lie to you if you let it.

If the engine has large enough cams, for instance an NA engine on carbs, La is useless until it comes out of 'idle mode' above 2500-3000 RPM (or more), it will read very lean but be correct, same issue can occur with a VVT system and moderately sized cams when at or near full intake advance, say below 100 deg ICL.

Point being La is not a sensor that can be trusted to tell the truth 100%.

[Holmz]

Holmz,
An answer to the "last question"....basically nothing. I have had a customer who saved some money by going wasted spark with a monster overlap cam (Cleveland V8) and at starting sometimes it tried to blow the intake manifold off.

Thanks Mark...
I guess not using wasted spark is the preferred option then?